I got tired of having to guess what the lambda controller was doing, so I decided to try to add a blower tachometer reading to my data logger. Since I have it running on a raspberry pi with lots of unused inputs and outputs available it's just a matter of getting a feedback pulse from the fan. I build a simple and cheap optical sensor with an IR-led and a matching IR detector, which turned out to work perfectly right away.
Now I finally can be sure about the setting called 'FORSTÆRKNING I'. As I have suspected it is a pure derivative term and not an integrating term (despite it's name). The oxygen controller for the blower is thus a PD controller.
In the graph above I have P and D set to "a large value" up to 13:47
Then only P up to 14:04 (D=0)
Then up to 14:15 both P and D are 0
and finally after 14:15 only the D term is active
Which all makes it quite obvious that it is a PD controller.
(This is on a V6.33)
As always the code is freely available at
https://github.com/motoz/PellMon
